With the advent of inexpensive digital storage, recording bound documents in a digital format is an important way of preserving information in books, periodicals, manuscripts, or any other document having a bound edge with a hard or soft cover. Content of a page of a bound document is first scanned and then electronically recorded. The recorded digital image can then be manipulated or processed to enhanced forms not originally available in its bound format. For example, digital images recorded on a storage medium can be reproduced audibly using applications that generate speech from ASCII text. Alternatively, bound documents digitally recorded can be reformatted or enhanced with additional information and reproduced on demand as hardcopy using an electronic printing machine such as a laser or ink jet printer.
In order to minimize the stress on the spine of bound documents when capturing or copying image content, wedge or angled platens of scanners and copying machines have been developed. For example, U.S. Pat. No. 3,888,584 to Smith, U.S. Pat. No. 4,068,950 to Kito, and "Book Copying Apparatus," by V. Agarawal, Xerox Disclosure Journal Vol. 9, No. 6, November/December, 1984, p. 383, disclose arrangements for scanning a book on a platen supported horizontally with respect to a support surface. Specifically, an edge of the support surface is arranged to meet a side wall in order that a bound document can be draped over the side of the scanner. While some arrangements provide support for a bound document with a wedge platen having an angle of approximately ninety degrees, other arrangements provide support with wedge platens having angles less than or greater than ninety degrees. For example, Guenther discloses a wedge platen having an angle greater than ninety degrees in "Library Copier," Xerox Disclosure Journal Vol. 12, No. 5, September/October, 1987, pp. 231-232. Alternatively, UK Patent Application GB 2 158 599A, published 1985 to Kobayashi, discloses an electrophotocopier with a wedge platen that is less than ninety degrees.
A principal function of wedge or angled scanning surfaces is to prevent damage to a bound document by minimizing stress applied to its binding as it is held open for scanning in a position as close to the platen of a scanner as possible. Typically when using a flat-bed scanner, a force has to be applied the spine region of a bound document to insure that the document is within the scanner's depth of focus. A wedge or angled platen, however, positions the spine region of a bound document within the scanner's depth of focus without requiring the application of additional force to the document's binding. U.S. Pat. Nos. 4,980,720 and 5,276,530 to Siegel disclose a book scan mode for a flat-bed scanner which minimizes the force typically required to be applied to a binding. In the book scan mode, a page height detector mounted on a scan carriage accounts for the deviation of the book pages from the horizontal platen plane. Alternatively, U.S. Pat. No. 5,475,505 to Minasian et al. discloses a combination flat-bed scanner and wedge shaped scanner. Specifically, Minasian et al. discloses a canted platen input scanner with an adjustable housing support. In a first position, the housing support is canted to facilitate scanning of bound documents, and in a second position the housing support brings the platen to a horizontal position to facilitate scanning other classes of documents.
Additional examples of wedge platens for scanning bound documents include, U.S. Pat. No. 5,359,207 to Turner, German Patent DE-A1 3546404, and U.S. Pat. Nos. 4,585,334 and 4,645,332 to Malyon. Turner discloses a book scanner with contact imaging that employs two-dimensional sensor arrays that are attached at a common edge and disposed in a wedge shaped manner. German Patent DE-A1 3546404 discloses a roof-shaped book support apparatus for use in a copier application. The optics of the roof-shaped copier arrangement provide that opposing pages of a bound book are simultaneously imaged in the same image plane. Consequently, the roof-shaped book support apparatus must have an sensing area large enough to capture two pages of a bound document at a time. In addition, the roof-shaped copier arrangement adjusts the spacing of the images of both pages in the image plane without having to change the position of the book. Malyon discloses a photocopying device with a V-shaped book rest for supporting and scanning a book in an open condition.
In order to facilitate the copying or reproduction of bound documents a plurality of automatic page taming apparatuses have been developed. Such page mining apparatuses minimize the amount of manual effort required to electronically capture the contents of a bound document. By way of example, U.S. Pat. No. 4,663,873 to Shinbrot, U.S. Pat. No. 5,390,033 to Bannai et al., and U.S. Pat. No. 5,471,277 to Fujioka et al. disclose arrangements for turning pages of a book within a copier. Other page turning arrangements include U.S. patent application Ser. No. 08/570,880 entitled "Bound Document Imager with Page Turner" to Turner et al., filed on Dec. 12, 1995 and assigned to the same assignee as the present invention, and U.S. patent application Ser. No. 08/570,791 entitled "Bound Document Imager with Air Jet Page Turning System" to Turner et al., filed on Dec. 12, 1995 and assigned to the same assignee as the present invention.
Further advances have been made to electronic publishing systems to offer job programming of books on a flat bed scanning system. U.S. Pat. No. 5,119,206 to Rourke et al. discloses a system for printing bound documents. The system can be programmed to scan either a selected side or both sides of the bound document. The attached printing system can then be programmed to print both sides of a page on a common print media sheet or on separate print media sheets. U.S. Pat. No. 5,212,568 to Graves et al. discloses an electronic reprographic apparatus that selectively controls the areas of the document to be imaged. The system enables the user to identify the type of input document so that the potential of imaging beyond document edges or in bound document gutter regions is eliminated.
All references cited above are incorporated herein by reference where appropriate for appropriate teachings of additional or alternative details, features, and/or technical background.
Although the aforementioned wedge scanning systems reduce stress applied to bound edges of documents, most wedge scanning systems scan a single page of a bound document at a time and require that the bound document is repositioned before the opposing page is scanned since only one face of the wedge scanning system is used to record image dam. In contrast, other scanning systems such as that disclosed in German Patent DE-A1 3546404 do not require repositioning a bound document in order to image both sides. However, such a scanning system requires an image sensing area sufficiently large to simultaneously capture both pages of the bound document. Similarly, the aforementioned wedge contact scanning system disclosed by Turner requires two two-dimensional flat panel detectors to image opposing pages of a bound document without having to repositioning it in order to scan both sides. In addition, such contact imaging arrangements have a reduced depth of focus since it is difficult to provide contact sensors with thin yet durable surface protection. Accordingly, it would be desirable to provide a wedge scanning system with an increased depth of focus. In addition, it would be desirable to provide a wedge scanning system that does not require repositioning a bound document while sequentially imaging opposing sides of the bound document using a sensing area that captures a single opposing page of a bound document at a time.